This project concerns characterization of the surface components of a recently defined veterinary pathogen: the causative agent of contagious equine metritis (CEM). CEM is a sexually transmitted venereal disease of horses; the etiological agent is an unclassified gram-negative diplococcus which shares several morphological and biochemical characteristics with Neisseria species. In addition, the disease profile of CEM bears some resemblance to gonorrhea in humans. Continued studies focus on (1) evaluation of colony morphology, (2) evaluation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of outer membrane constituents: lipopolysaccharide, capsular polysaccharide and proteins, and (3) evaluation of antigenic composition of surface constituents using hyperimmune rabbit sera and equine immune sera from experimentally infected animals.